The blow molding refers to a process of molding a hollow product by clipping, with a blow mold, a hollow pipe-shaped thermoplastic molten discharged material (hereinafter, referred to as parison) discharged from an extrusion die and by blasting a blow air inward of the in-mold parison.
As a method of delivering the parison to the blow mold, there is described a related art in PTL 1 shown below in which simultaneously when a parison extrusion-molded vertically downward is pinched at near its lower end by a lower chuck, the parison is cut and pinched concurrently at a portion between the lower chuck and a molding die by a cutting edge-equipped upper chuck, and then the molten parison, while held by the upper-and-lower chucks, is moved horizontally as it is so as to be inserted into the mold for blow molding. On the way of the insertion, the lower chuck is moved downward so that a sag of the molten parison due to its drawdown is absorbed while a thinner parison is made at the same time. The parison is then delivered to the blow mold.